1. Field of the Invention
The invention relates to a projection apparatus, and more particularly to an adjusting apparatus that uses to adjust a mirror in the projection apparatus.
2. Description of the Related Art
In a projection apparatus, optical elements have to be precisely assembled for reflecting a projecting light beam at a predetermined angle and generating clear image frame without image deformation or aberration.
Referring to FIG. 1, an optical system of a conventional rear projection television 10 includes a casing 11, a base 12, a base frame 13 mounted on the base 12, and an optical engine 14 mounted on the base frame 13. A first mirror 15 is fixed in front of the optical engine 14 via a fastener 152 of a holder 151, and a second mirror 17 is disposed on the inner side of a rear cover 111. The light beam emitted from the optical engine 14 is projected onto the first mirror 15. The beam is then reflected onto the second mirror 17 from the first mirror 15, and finally is projected onto a screen 16, which constitutes the optical system.
In order to ensure that the first mirror 15 is positioned at a correct position relative to other optical elements of the rear projection television 10, the conventional optical elements should be had precision tolerance in manufacturing and assembling so as to increase the manufacturing cost of optical elements of the rear projection television 10. According to other approaches known in the art, a plurality of bolts 153 can be fastened onto the fastener 152 being used to fix the first mirror 15. The position of the first mirror 15 is adjusted by rotating the bolt 153. The first mirror 15 can be moved in a specific direction by manipulation of the adjusting means. The adjustment of the first mirror 15 can be done within a limited range, and does not simplify the assembly of the rear projection television 10.
One object of the invention is to provide an adjusting apparatus for projection, in which a first mirror can be quickly positioned at a proper position with an exact projection angle via adjusting a ball bearing and an adjusting bolt in various directions.
Another object of the invention is to provide an adjusting apparatus for projection, in which a first mirror can be shifted along its axial direction to increase the freedom of the first mirror.
In order to achieve the above and other objectives, an adjusting apparatus for projection comprises a carrier having a central screw hole and three rounded indentations around central screw hole, an adjusting frame having a plane section and base section connecting to the plane section, and a holder. The center of the plane section has a circular concave dug a hole with a smaller aperture. A ball bearing is accommodated in the circular concave. The plane section has three screw holes corresponding to the rounded indentations. Three angle-adjusting bolts respectively insert through the screw holes to abut against the rounded indentations. Rotating the angle-adjusting bolts relative to each other varies the length of the angle-adjusting bolts calculated from the plane section of the adjusting frame to the carrier. Thereby, an angle adjustment of a mirror is achieved. Furthermore, the plane section has an adjusting hole at its lower side. A retainer having a through hole externally extends from a top of the holder. One end of a spring is blocked by the retainer, and the other end of the spring is inserted into the adjusting hole. A shift-adjusting bolt inserts through the through hole and the spring, and screws to the adjusting hole. Thus, rotating the shift-adjusting bolt can achieve shifting adjustment for the first mirror. The base section has at least one slot corresponding to a positioning screw hole of the holder for guiding. At least one positioning bolt inserts through the slot to fix the adjusting frame to the holder.